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In this report, we described the genome of a novel baculovirus isolated fromthemonocot insect pestMocis latipes, the striped grass looper. The genome has 134,272 bp in length with a G + C content of 38.3%. Based on the concatenated sequence of the 38 baculovirus core genes, we found that the virus is a betabaculovirus closely related to the noctuid-infecting betabaculoviruses including Pseudaletia unipuncta granulovirus (PsunGV), Trichoplusia ni granulovirus (TnGV), Helicoverpa armigera granulovirus (HearGV), and Xestia c-nigrum granulovirus (XecnGV). The virus may constitute a new Betabaculovirus species tentatively named Mocis latipes granulovirus (MolaGV). After gene content analysis, five open reading frames (ORFs) were found to be unique to MolaGV and several auxiliary genes were found including iap-3, iap-5, bro-a, bro-b, and three enhancins. The virus genome lacked both chitinase and cathepsin. We then looked at the evolutionary history of the enhancin gene and found that betabaculovirus acquired this gene from an alphabaculovirus followed by several duplication events. Gene duplication also happened to an endonuclease-like gene. Genomic and gene content analyses revealed both a strict collinearity and gene expansion into the genome of the MolaGV-related species. We also characterized the granulin gene using a recombinant Autographa californica multiple nucleopolyhedrovirus (AcMNPV) and found that occlusion bodies were produced into the nucleus of infected cells and presented a polyhedral shape and no occluded virions within. Overall, betabaculovirus genome sequencing is of importance to the field as few genomes are publicly accessible. Mocis latipes is a secondary pest of maize, rice, and wheat crops in Brazil. Certainly, both the discovery and description of novel baculovirusesmay lead to development of greener and safer pesticides in order to counteract and effectively control crop damage-causing insect populations. [ABSTRACT FROM AUTHOR]

Enhancins are metalloproteinases that facilitate baculovirus infection in the insect midgut. They are more prevalent in granuloviruses (GVs), constituting up to 5% of the proteins of viral occlusion bodies (OBs). In nucleopolyhedroviruses (NPVs), in contrast, they are present in the envelope of the occlusion-derived virions (ODV). In the present study, we constructed a recombinant Autographa californica NPV (AcMNPV) that expressed the Trichoplusia ni GV (TnGV) enhancin 3 (En3), with the aim of increasing the presence of enhancin in the OBs or ODVs. En3 was successfully produced but did not localize to the OBs or the ODVs and accumulated in the soluble fraction of infected cells. As a result, increased OB pathogenicity was observed when OBs were administered in mixtures with the soluble fraction of infected cells. The mixture of OBs and the soluble fraction of Sf9 cells infected with BacPhEn3 recombinant virus was ~3- and ~4.7-fold more pathogenic than BacPh control OBs in the second and fourth instars of Spodoptera exigua, respectively. In contrast, when purified, recombinant BacPhEn3 OBs were as pathogenic as control BacPh OBs. The expression of En3 in the soluble fraction of insect cells may find applications in the development of virus-based insecticides with increased efficacy. [ABSTRACT FROM AUTHOR]

Current knowledge of the field resistance of codling moth (CM, Cydia pomonella, L) against Cydia pomonella granulovirus (CpGV) is based mainly on the interaction between the Mexican isolate CpGV-M and CpRR1, a genetically homogeneous CM inbreed line carrying type I resistance. The resistance level of laboratory-reared CpRR1 to CpGV-M was recently found to have decreased considerably, compared to the initially high resistance. To understand the background of this phenomenon, CpRR1 larvae were exposed over several generations to CpGV-M for re-selection of the original resistance level. After five and seven generations of selection, new CpRR1_F5 and CpRR1_F7 lines were established. The resistance ratio of these selected lines was determined by full range bioassays. The CpRR1_F5 strain regained a higher level of resistance against CpGV up to 104-fold based on LC50 values compared to susceptible larvae (CpS), which indicated that the absence of virus selection had resulted in a reduction of resistance under laboratory rearing conditions. In addition, some fitness costs of fecundity were observed in CpRR1_F5. Single-pair crossings between CpRR1_F5 or CpRR1_F7 with susceptible CpS moths revealed a dominant but not fully sex-linked inheritance, which suggests a partial loss of previous resistance traits in CpRR1. [ABSTRACT FROM AUTHOR]

Virus infections of insects can easily stay undetected, neither showing typical signs of a disease, nor being lethal. Such a stable and most of the time covert infection with Phthorimaea operculella granulovirus (PhopGV) was detected in a Phthorimaea operculella laboratory colony, which originated from Italy (Phop-IT). This covert virus (named PhopGV-R) was isolated, purified and characterized at the genetic level by full genome sequencing. Furthermore, the insect colony Phop-IT was used to study the crowding effect, double infection with other PhopGV isolates (CR3 and GR1), and co-infection exclusion. An infection with a second homologous virus (PhopGV-CR3) activated the covert virus, while a co-infection with another virus isolate (PhopGV-GR1) led to its suppression. This study shows that stable virus infections can be common for insect populations and have an impact on population dynamics because they can suppress or enable co-infection with another virus isolate of the same species. [ABSTRACT FROM AUTHOR]

Baculoviridae is a highly diverse family of rod-shaped viruses with double-stranded DNA. To date, almost 100 species have had their complete genomic sequences deposited in the GenBank database, a quarter of which comprises granuloviruses (GVs). Many of the genomes are sequenced using next-generation sequencing, which is currently considered the best method for characterizing new species, but it is time-consuming and expensive. Baculoviruses form a safe alternative to overused chemical pesticides and therefore there is a constant need for identifying new species that can be active components of novel biological insecticides. In this study, we have described a fast and reliable method for the detection of new and differentiation of previously analyzed granulovirus species based on a real-time polymerase chain reaction (PCR) technique with melting point curve analysis. The sequences of highly conserved baculovirus genes, such as granulin and late expression factors 8 and 9 (lef-8 and lef-9), derived from GVs available to date have been analyzed and used for degenerate primer design. The developed method was tested on a representative group of eight betabaculoviruses with comparisons of melting temperatures to allow for quick and preliminary granulovirus detection. The proposed real-time PCR procedure may be a very useful tool as an easily accessible screening method in a majority of laboratories. [ABSTRACT FROM AUTHOR]